The present invention relates in general to a water-repellent solution and a method of forming a water-repellent film by using the solution. More specifically, the present invention relates to a water-repellent solution which is applicable to vehicular and architectural window or mirror glass plates to form thereon a water-repellent film. Furthermore, the present invention relates to a method of forming a water-repellent film on such window or mirror glass plates by using the water-repellent solution.
Hitherto, various types of water-repellent solutions and methods of producing a water-repellent film on a glass plate by using the solutions have been proposed and put into practical use, some of which are described in Japanese Patent First Provisional Publications 9-132433, 9-309746, 3-247537, 58-122979 and 58-129082 and Japanese Patent 2,500,178.
However, due to their inherencies, the techniques disclosed and suggested by these publications have failed to give users satisfaction. That is, some of them need a troublesome and expensive handling process for producing the water-repellent solution and/or forming the water-repellent film on a glass substrate, and some of them fail to provide the glass substrate with a film which exhibits a satisfied performance in water repellency and durability.
It is therefor an object of the present invention to provide a water-repellent solution and a method of forming a water-repellent film by using the solution, which are free of the above-mentioned drawbacks possessed by the conventional techniques.
That is, it is an object of the present invention to provide a water-repellent solution which is suitable for forming a water-repellent film on a glass substrate, which is superior in water repellency, abrasion resistance and durability.
It is another object of the present invention to provide a method of forming such high performance water-repellent film on a glass substrate by using the water-repellent solution.
It is still another object of the present invention to provide a water-repellent layered article having such water-repellent film formed on a substitute.
It is a further object to provide a method of producing such water-repellent layered article.
According to a first aspect of the present invention, there is provided a water-repellent solution for application to a substrate to form on a surface thereof a water-repellent film. The solution comprises polymers of a fluoroalkyl-group contained silane compound, and the polymers include at least dimers and trimers.
According to a second aspect of the present invention, there is provided a method of forming a water-repellent film on a substrate. The method comprises the steps of: preparing a water-repellent solution, the solution being produced by subjecting a fluoroalkyl-group contained silane compound to a hydrolysis and a condensation polymerization thereby to produce at least dimers and trimers of the silane compound; applying the water-repellent solution to a surface of the substrate; and heating the substrate to cause the fluoroalkyl-group in the solution to be bonded to the surface of the substrate thereby to form the water-repellent film on the substrate.
According to a third aspect of the present invention, there is provided a water-repellent layered article which comprises a substrate; and a water-repellent film formed on a surface of the substrate. The film is prepared by applying a water-repellent solution to the surface. The water-repellent solution is prepared by subjecting a fluoroalkyl-group contained silane compound to a hydrolysis and a condensation polymerization. The fluoroalkyl-group contained silane compound is represented by the following general formula:
CF3(CF2)m(CH2)2SiX3 
wherein xe2x80x9cmxe2x80x9d is equal to or greater than 7 and xe2x80x9cXxe2x80x9d represents halogen, isocyanate-group or alkoxy-group, the alkoxy-group including methoxy-group [OCH3], ethoxy-group [OC2H5] or isopropoxy-group [OC3H5].
According to a fourth aspect of the present invention, there is provided a method of producing a water-repellent layered article. The method comprises the steps of preparing a water-repellent solution and a substrate, the solution being produced by subjecting a fluoroalkyl-group contained silane compound to a hydrolysis and a condensation polymerization; applying the water-repellent solution to a surface of the substrate; and heating the substrate to cause the fluoroalkyl-group in the solution to be bonded to the surface of the substrate thereby to form the water-repellent film on the substrate, wherein the fluoroalkyl-group contained silane compound is represented by the following general formula:
CF3(CF2)m(CH2)2SiX3 
wherein xe2x80x9cmxe2x80x9d is equal to or greater than 7 and xe2x80x9cXxe2x80x9d represents halogen, isocyanate-group or alkoxy-group, the alkoxy-group including methoxy-group [OCH3], ethoxy-group [OC2H5] or isopropoxy-group [OC3H5].